Electric alarm system



M. YAROW. ELfEc mc ALARM SYSTEM.

APPLICATION FILED OCT- I0, 1918- 1,335,707, Patented Mar 30 192 0.

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UNITED s'rArEs PA ENT OFFICE.

MAX YABOW, OF PHILADELPHIA, PENNSYLVANIA.

ELECTRIC ALARM SYSTEM.

- Specification of Letters Patent. Patented Mar, 30, 1920.

Application filed October 10, 1918. Serial No. 257,596.

To all whom it may concern:

Be it known that I, MAX YAROW, a citizen of the United States, residing at Philadelsever the wires to frustrate'a phone call for police assistance, an alarm will be sounded at central. The invention is also applicable to field phones to soundan alarm at the central station if the communicating wires should be cut by the foe or by an exploding shell.

In order that the invention may be better understood, reference is had to the accompanying drawingin which a diagrammatic representation of the invention is shown.

Referring specifically to the drawing 1 denotes an electric bell or other suitable electro-responsive signal device located at the central station and designedto notify central that a subscriber-or a distant station desires connection. The magnet which operates the bell obtains current from a battery or other suitable source 2. One side of this battery is connected by a conductor 3 to the bell magnet and from the latter a conductor 4: leads to a contact 5 at the distant station or subscribers house. This contact is engaged by the receiver hook 6 when the receiver is removed, and as the latter is con.- nected by a conductor 7 to the other side of the battery 2, it will be seen that the bell 1 is sounded when the receiver is lifted oil the hook. The parts thus far described constitute the ordinary calling circuit of a telephone system and a further description thereof is not deemed necessary. The other parts of the system have not been illustrated as they are well known and form no part of the present invention. The calling circuit is normally open. v I

At central is located a relay 8 which is energized by a battery or other current source 9 located at the distant station. One

side of this battery is connected by a conductor 10 to the relay, and the other side of the battery is connected by a conductor 11 to the conductor 7. A branch conductor'12 from the conductor 7 also leads to the relay. The circuit of therelay istherefore as follows: battery 9, conductor 10, relay 8,

conductor '12, conductor 7 and conductor 11 back to battery. The relay circuitis normally closed, and'hence the armature 13 is held attracted against the tension of a spring let. From the conductor 12, a conductor 15 makes connection with the armature 1 3, and back of thelatter is a contact l6'which is connected by a conductor 17 to the conductor 4. The armature 13 is oil the contact 16 when the relay 8 is energized, and when the relay circuit is broken, the spring 14 draws the armature 13 over against the contact 16, whereupon a local circuit is established andthe hell 1 is sounded. This circuit may be traced as follows: one side of battery 2 by conductor 3 to bell 1, conductor 1, conductor 17, contact'16, armature 13,: conductor 15, conductor 12 and by conductor 7 to other side of battery 2. It will be evident from the foregoing that if the conductors 10, or 7 should be severed from any cause, the

relay circuit will be broken, whereupon the local circuit through the bell 1 is established and the latter is sounded, and the continued ringing of the bell would indicateto central that the line to the subscribers or the distant station was cut.

I claim: j

The combination with the calling circuit of a telephone line, including an electrodesponsive signal device at central, and a current source interposedfin said circuit; of a relay, branch conductors connected to the calling circuit on one side 7 of its current source and connected to the relay magnet, a current source interposed in one of the branch conductors to energize the relay magnet, a connection from the other branch conductor to the armature of the relay magnet,

a contact opposite said armature, and a con MAX YAROW. 

